23 November 2011

Excellent Coverage of SBSP from Aviation Week!

Conventional wisdom typically holds that harvesting “free” energy from the Sun with giant collectors in space does not make financial sense, at least until Earth’s finite supplies of oil, coal and natural gas become so scarce that there’s no other choice. The conventionally wise usually suggest that it will make more economic sense to rely on wind power and ground-based solar cells for “green” renewable energy. But now a panel of the International Academy of Astronautics (IAA), an elite organization of scientists, engineers and other experts who collectively examine some of the big issues of space exploration, has concluded that spacesolarpower (SSP) could start paying for itself in as little as a decade.
John Mankins, a leading SSP visionary, co-chaired the IAA panel with Nobuyuki Kaya of Japan’s Kobe University, where a lot of the technical ground for SSP already is being broken. They presented their findings at the National Press Club in Washington on Nov. 14, after unveiling them at the International Astronautical Congress in Cape Town, South Africa, last month. Examining various SSP approaches and four scenarios for the way global energy needs will influence the world economy, the IAA panel concluded that “premium niche markets” could support SSP profitably in the relative near term, particularly if some new approaches to assembling the big space-based collectors are followed. Technical hurdles that remain to be surmounted include thermal control, either with better spaceradiators or higher-temperature electronics. But the SSP idea is more attractive now that at any time since it first was conceived in the late 1960s.

“There has been general consensus in every study, both here and abroad, that spacesolarpower is technically feasible, that there are no show-stoppers,” says Mark Hopkins, CEO of the National Space Society, which sponsored a panel discussion of the IAA report at the press club. “But this is the first major study which has come out and said there’s a good chance it can be economically viable.”
Mankins says the study examined three “promising” SSP concepts for positioning in geostationary orbit—a stabilized platform using solar arrays like those on the International Space Station to generate electricity converted to microwaves for transmission to large rectifying antennas (rectennas) on Earth; a modular approach linking solar arrays and lasers beaming down power in near-visible wavelengths, and a modular approach concentrating solar energy with large mirrors before converting it to microwaves.
The stabilized platform was studied in depth in 1979, Mankins says, and is no longer attractive because it is limited to about 100 kw without being “fundamentally rearchitectured.” The laser approach runs into efficiency issues in competition with other power-generation systems above 100 mw, according to the IAA, while the modular “sandwich” microwave architecture is the most promising because it is scalable.“One of the things which appears very promising now is the idea that through these hypermodular architectures, that you can build fairly tractably, with tens of millions of dollars, a prototype of a module,” Mankins says. “And for a bit more money you can make a bunch of copies of those modules.”
The microwave approach will require more work on thermal control, Mankins said, and any large structure will require advances in on-orbit assembly, in-space propulsion and, ultimately, launch vehicles. But at least initially a 10-mw system costing $10 billion, of the type already considered by the Pentagon for supplying power to forward-deployed bases and disaster areas, probably could be launched with existing or planned vehicles like the Delta IV Heavy and Falcon 9 Heavy, respectively.
The IAA panel concluded that for the rest of the century, growing demand for electricity will call for many new sources of energy. Wind and terrestrial solarpower will help, but unlike SSP are subject to local weather conditions. Space-generated power, by contrast, can be beamed to areas where weather is temporarily stilling windmills and blocking sunlight, Mankins says.
The IAA report does not assume that SSP will totally replace other sources of electricity, but finds it can gradually assume a larger role as the global population grows from 7 billion to twice that by century’s end. U.S. military strategists have long seen SSP as an alternative to the “energy wars” they fear as fossil fuel supplies dwindle, while development of SSP technology will place the nation or nations that control it in a strong position to shape geopolitics. Another benefit may come with the jobs generated by large-scale SSP production.
“If you think about the skill set that is necessary to build a system like Orbcomm or GPS, it’s that same kind of skill set, but a lot of them,” Mankins says. “At full scale by mid-century, spacesolarpower is like the automotive industry, meaning you have a very large and high-tech workforce and a set of infrastructure with factories building pieces of solarpower satellites. The reasonable number [for SSP generating 100-200 gw] works out to millions of jobs.”